1. Field of the Invention
The invention relates to a magnetic coupling device which is used for charging an electric vehicle by using electromagnetic induction.
2. Description of the Related Art
Recently, a system of the noncontact type which uses the electromagnetic induction as described above was developed. An example of such a system is disclosed in Japanese Patent Unexamined Publication No. Hei. 5-258962. In the disclosed system, as shown in FIG. 27, a secondary unit 1 is disposed on the body of an electric vehicle, a primary unit 6 connected to a charging power source 5 is set to the secondary unit 1 so as to attain the electromagnetic coupling state, and an AC current is then supplied to the primary unit 6, thereby generating an power on the side of the secondary unit 1.
In the system of the .related art, the secondary unit 1 is configured by forming a pair of case-like cores 2 in each of which one face is opened and a pair of secondary coils 3 housed therein, and causing the opened faces of the case-like cores 2 to oppose each other via a gap for inserting a primary coil 7.
Therefore, the secondary unit 1 requires the two sets of the core 2 and the secondary coil 3. This produces a problem in that the whole of the magnetic coupling device is large and heavy.
Furthermore, the coils 3 and 7 are coupled to each other by slidingly inserting the primary coil 7. Consequently, the secondary unit 1 must have a structure in which an insertion stroke is ensured so as to have a depth which corresponds at the minimum to the length of the primary coil 7. As a result, the depth of the secondary unit 1 which is to be disposed on a vehicle is increased, thereby producing a problem in that the magnetic coupling device is large as a whole.
In the configuration, the whole of the primary coil 7 is exposed. During a period when the device is handled in order to charge an electric vehicle, therefore, the coil is easily damaged. This produces another problem in that a countermeasure for protecting the coil must be taken.
Further, after the primary coil 7 is set to the secondary unit 1, by closing the gap between the pair of the case-like cores 2 by a switching device (not shown), the electromagnetic coupling state is attained. Therefore, the switching device has to be provided in the electric vehicle side, thereby causing the increase of the size of the magnetic coupling device in the electric vehicle side.